Talenkauen
Talenkauen (meaning "small skull" inAonikenk, referring to the proportionally small skull) is a genus of basal iguanodont dinosaur from theCenomanian-age1 Upper CretaceousPari Aike Formation of Lake Viedma,Santa Cruz, Argentina. It is based onMPM-10001, a partial articulated skeleton missing the rear part of the skull, the tail, and the hands. Its most unusual feature is the presence of several thin mineralized plates along the sides of the ribs.2 Description￼ Alternate view of skeleton Talenkauen was rather like Dryosaurus in shape and build, but with a proportionally longer neck. The full length of the body is estimated at no more than 4 meters (13 feet). Unlike more derived iguanodontians, it still hadteeth in the tip of the beak (premaxillaryteeth), and a first toe. More derivediguanodonts lose this toe, retaining only the three middle toes. The humerus has reduced areas for muscle attachment, a featured shared with other South American ornithopods like''Notohypsilophodon'' and Anabisetia. This and other similarities to South American ornithopods suggests that there may have been a distinct Southern Hemisphere ornithopod group, but at the time the authors cautioned that such an interpretation was not entirely justified. In 2015, the describers of''Morrosaurus'' found that such a clade did indeed exist.3 Mineralized plates Talenkauen's most distinct feature is a set of smooth, ovoid plates found along the side of the rib cage. These plates can be long (180 millimeters, or 7.1 in), but are very thin (only 3 millimeters thick in). They were present with at least the first eight ribs, attaching along the middle portion of a rib and lying flat.2 Several other dinosaurs are known to have had similar plates, including Hypsilophodon, Othnielosaurus,Parksosaurus, Thescelosaurus,4 and''Macrogryphosaurus'' (also from Argentina, but from somewhat older rocks), which may have been related.5Because of the fragility of the plates, and the fact that they may not have always turned to bone in the living animal, they may have been more widespread than currently known. Novas and colleagues suggested that the plates may be homologous touncinate processes, strip-like bony projections found on the ribs of a variety of animals including the tuatara,crocodiles, birds, and somemaniraptoran theropod dinosaurs. In birds, uncinate processes help to ventilate the lungs, working with rib cage muscles, and Novas and colleagues proposed a similar function for the plates of Talenkauen.2 This homology was rejected in a more recent study by Richard Butler and Peter Galton because of the plates' form.4The plates were too thin and limited in location to have been very useful as defensive devices. Paleobiology Talenkauen, as a basal iguanodont, would have been a small, bipedalherbivore.6 Other dinosaurs from the Pari Aike Formation include the gianttitanosaurid Puertasaurus7 and the predatory neovenatorid Orkoraptor.8 Classification Through cladistic analysis, it was found to be more basal than Dryosaurus and''Anabisetia'', but more derived than''Tenontosaurus'' and Gasparinisaura.2More recently, the describers of''Macrogryphosaurus'' found their genus and Talenkauen to be related, and coined the clade Elasmaria for the two genera.5 In 2015, several other Patagonian and Antarctic ornithopods were also found to be related.3 Cladogram based in the phylogenetic analysis of Rozadilla et al., 2015: |- | |} |- | |- | | rowspan="2" | |} |} |} |} |} |} |} Category:Small Herbivores Category:Small dinosaurs Category:Cretaceous dinosaurs Category:Taxa named by Fernando Novas Category:Fossil taxa described in 2004 Category:Iguanodonts Category:Dinosaurs of South America